The present invention relates to an electrochemical power generator which generates power by using a gas consisting mainly of hydrogen as an anode-active material, a gas such as oxygen having oxidizing power as a cathode-active material, and an acidic solution as an electrolyte.
An electrochemical power generator is known which causes the generation, as DC power, of Gibb's free energy developed in an electrochemical reaction between a gas, such as hydrogen, which is capable of being easily oxidized, and an oxidizing gas, such as oxygen. It is well known to those in the art that this type of power generator is high in generating efficiency, causes very little noise, and produces less undesirable discharge. For obvious reasons, such a power generator has recently attracted a great deal of attention as a suitable power generator for power plants to be built in densely populated regions.
A power generator prepared by stacking a large number of unit cells 8, as shown in FIG. 1, is conventionally known as the above-mentioned power generator. In FIG. 1, the unit cell 8 is made up of: a cathode 4 consisting of a porous carbon thin plate made of graphite fiber and having a cathode catalyst layer 3 provided on its one side, an anode 7 having an anode catalyst layer 6 provided on its one side, and an electrolyte layer 1 interposed between the cathode and anode catalyst layers 3, 6, with said cathode and anode and electrolyte layers being adhered to each other for integration. The electrolyte layer 1 is formed of a material which is high in heat resistance, chemical resistance and oxidation resistance, and is impregnated with an electrolyte solution such as concentrated sulfuric acid solution, concentrated phosphoric acid solution or the like. Platinum or the like is used as a catalyst contained in the catalyst layers. The cathode 4 and the anode 7 are subjected to a waterproofing treatment based on the use of polytetrafluoroethylene or the like.
Since an electromotive force produced in the unit cell 8 having said construction has a value of around 1 V at the most, unit cell arrays as large as several tens or several hundreds of unit cells are required to be stacked and connected to each other in series in order to realize a practical power generator. In the prior art, when the unit cells are stacked, an interconnector 11 consisting of a conductive carbon plate, or a molded graphite plate of high density, is interposed between each unit cell 8 for electrical connection between each unit cell 8. On one surface of the interconnector 11, namely that surface which comes into contact with cathode 2, there are formed in parallel a large number of grooves 9 for permitting the flow therethrough of an oxidizing gas; and on the other surface of the interconnector 11, namely the surface thereof which comes into contact with anode 5, there are formed a large number of grooves 10 for permitting the flow of a gas containing hydrogen gas, in such a manner that the grooves 10 extend in parallel in a direction perpendicular to the direction in which the grooves 9 extend. It is to be noted here that a large number of the interconnectors 11 are disposed such that the direction in which the grooves 9 or 10 extend is made the same with respect to each interconnector 11. Further, the grooves 9, 10 are provided in large number and with narrow ribs 14, 13 between the grooves for the purpose of distributing a gas as an active material uniformly and with high efficiency onto the entire corresponding surface of the cathode and anode and at the same time removing the reaction products with high efficiency.
In the electrochemical power generator constructed as mentioned above, a sufficient feeding of the reacting gases onto the surfaces of the cathode and anode as well as a speedy removal of the reaction products is necessary to maintain the high performance of the power generator for a long period of time. Further, ensuring high electrochemical reactivity as well as maintaining the internal ohmic loss of the unit cells at a low level is important for maintaining high generating efficiency of the power generator. Further, when a large number of the unit cells are stacked with the interconnectors interposed therebetween, the unit cells and the interconnector must be fastened together uniformly and with high mechanical strength to ensure uniform surface-contact between the unit cell and the interconnector.
Since, however, the prior art power generator shown in FIG. 1 is constructed such that the cathode, anode and interconnector are made thin so as to maintain a small internal ohmic loss in the cells, there arises a problem that the amount of electrolyte solution held in the cell is not sufficient, resulting in a drawback that the resultant power generator cannot perform long-term operation. Further, in the above-mentioned prior art power generator, the cathode and anode are substantially the same in construction. That is, the fact that a difference exists between the cathode and the anode with respect to the gas diffusion and the reaction rate is not taken into consideration. Accordingly, the construction of the prior art power generator fails to obtain a high electrochemical reactivity with high reliability. Further, the prior art power generator has a drawback in that it is impossible to ensure sufficient surface-contact between the unit cell and the interconnector, thus failing to obtain a uniform current distribution. Further, the unit cell and the interconnector are difficult to fasten with uniform mechanical force, possibly leading to damage to the anode and cathode which are quite thin.